16.3 Autoionization of Water

• Water undergoes autoionization:

  H2O + H2O ? H3O+ + OH-
  

• Kw = [H3O+][OH-] = 1.0 x 10-14 at 24oC

  Called the ion product of water
  

• By convention, [H2O] is omitted.

• In pure water, [H3O+] = [OH-] = 1.0 x 10-7 M

• Add an acid, [H3O+] > [OH-]

  0.10 M HCl (strong acid, completely ionized)
  
  [H3O+][OH-] = 1.0 x 10-14
  (0.10)[OH-] = 1.0 x 10-14
  [OH-] = 1.0 x 10-14 /0.10 = 1.0 x 10-13 M

Kotz CD: 17m03an1.mov

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